Capillary array electrophoretic device and auto sampler used for the device

ABSTRACT

A capillary array electrophoretic device capable of securing a sample plate array and a buffer container three dimensionally on a tray of an autosampler. A tray ( 700 ) is provided with a guide groove ( 701 ) and a stopper ( 702 ) corresponding to guides ( 715, 716 ) of sample plate assemblies ( 710, 711 ) including a microtiter plate.

TECHNICAL FIELD

[0001] The present invention relates to an electrophoretic device forseparating or analyzing samples such as DNA or proteins byelectrophoresis using a capillary array consisting of a plurality ofcapillaries bundled together, and to a sampling apparatus used therefor.

BACKGROUND ART

[0002] In a well-known technique for separating or analyzing samples tobe investigated, a capillary array is constructed by combining aplurality of capillaries, and then the samples to be analyzed orseparated are supplied to each capillary together with anelectrophoresis medium. Samples supplied to the capillaries include DNAlabeled with a fluorescent substance and proteins. Such a technique isdescribed in U.S. Pat. Nos. 5,366,608, 5,529,679, 5,516,409, 5,730,850,5,790,729, 5,582,705, 5,439,578, and 5,274,240, for example. From theviewpoint of separation or analysis throughput, use of multiplecapillaries can provide more advantages than the electrophoresis methodusing a slab gel.

[0003] A multicapillary array electrophoretic device includes a casinghousing a constant-temperature bath for storing the capillary array in aconstant temperature environment, a gel pump unit for replacing a gelpolymer as a separating medium in the capillary array, anirradiation/detection unit for irradiating the capillary array withlaser light or the like to detect fluorescence from fluorescence-labeledsamples, and an autosampler for continuously measuring many samples, forexample. An electrode is formed on one end (sample loading end) of thecapillary array to which a negative voltage can be applied. When DNA isinjected into the capillaries, the autosampler is moved so that thenegative electrode is submerged in a solution mounted on the autosamplerthat contains samples, and then a voltage is applied. Whenelectrophoresis of the injected samples is carried out, the negativeelectrode is submerged in a buffer solution mounted on the autosampler,and then a voltage is applied. The DNA samples and the buffer solutionare mounted on a tray on the autosampler. The samples are often put in ageneral-purpose microtiter plate capable of storing many samples atonce, which is then combined with a dedicated adapter or the like andmounted on the tray. The buffer solution is put in a buffer reservoirintended for that purpose which is mounted on the tray. The microtiterplate and the buffer reservoir are covered with septa for preventing theevaporation of the samples. The septa are provided with slits forallowing the insertion of capillaries.

[0004] The microtiter plate and the buffer reservoir are thus simplyplaced on the tray of the autosampler such that they are fixed in X andY directions but not in Z direction. As a result, when the autosampleris moved downward and the sample loading end of the capillary array isremoved from the wells in the microtiter plate or the buffer reservoir,the microtiter plate or the buffer reservoir could be lifted by thecapillary array due to the friction between the array and the septa.

[0005] In order to prevent this, conventionally a press-down plate (tobe hereafter referred to as a “stripper plate”) is used. The stripperplate can be moved up and down along the sample loading end of thecapillary array. For example, when a sample is introduced into thecapillary array, the autosampler is initially moved in X and Ydirections so as to position a target well directly below the capillaryarray where the sample loading end of the capillary array can beinserted into the well in the microtiter plate containing the sample.The autosampler is then moved upwards, when the stripper plate comesinto contact with the autosampler and is lifted. The stripper plateexerts a force pushing the microtiter plate downward provided by aspring secured to the stripper plate or by its own weight. Thus, whenthe autosampler is moved downward, the microtiter plate is pressedagainst the tray on the autosampler until the capillary array iscompletely pulled out, thus preventing the lifting of the microtiterplate.

[0006] However, this technique using the stripper plate has severalproblems. During sample introduction or electrophoresis, for example, adownward force is exerted on the autosampler as long as the stripperplate is in contact with the autosampler. The autosampler is driven by astepping motor, for example. Therefore, the autosampler is preventedfrom dropping by the static torque provided by the stepping motor aslong as it is energized. When the motor is not energized, however, thereis the danger of the autosampler being dropped due to the force providedby the stripper plate. For example, when the power to the device isturned off and the device is placed in a standby mode, it is necessaryto keep the sample loading end of the capillary array submerged in thebuffer reservoir or a water reservoir so as to prevent the drying of thecapillary array attached to the device. However, as the stepping motoris not energized in this mode, the autosampler could be dropped as it ispushed by the stripper plate. A similar problem could occur when thedoor of the device is opened by the operator during electrophoresis orwhile the autosampler is moving, because opening of the door requiresall the operations to be automatically stopped and various powersupplies to be shut down. It is of course possible to design the devicesuch that the autosampler would not be dropped unless it is pushed downwith a force sufficiently greater than the stripper plate. This,however, would greatly inconvenience the maintenance or servicingoperations where the autosampler would have to be moved manually.

[0007] Further, during sample introduction or electrophoresis, a highvoltage of the order of several to several tens of kV is applied to thesample introduction end of the capillary array. As a result, there isthe danger of discharge from the array electrode portion to the devicechassis via the stripper plate.

[0008] These problems become increasingly pronounced as the number ofcapillaries in the capillary array increases, thus posing a majorobstacle in increasing the throughput of the device.

[0009] Further, while the capillary array in its entirety is retained inthe constant temperature bath for maintaining the array at a certaintemperature, the sample loading end must be exposed outside the bath.The presence of a stripper plate makes it necessary to increase thelength of the capillary portions that are outside the constanttemperature bath, thereby adversely affecting the performance ofelectrophoresis.

[0010] It is therefore an object of the invention to provide a capillaryarray electrophoretic device capable of automatic operation without theuse of a stripper plate.

SUMMARY OF THE INVENTION

[0011] In order to achieve the aforementioned object of the invention, asample container such as a microtiter plate and a buffer reservoircontaining a buffer solution are secured on an autosampler not only inXY plane but also in Z direction, thereby enabling automatic operationof a capillary array electrophoretic device without the use of astripper plate.

[0012] The invention provides a capillary array electrophoretic devicecomprising: a capillary array made up of a plurality of capillaries withtheir sample injection ends arranged in order; a constant temperaturebath for storing the capillary array with the sample injection endsdisposed downward and exposed; and an autosampler comprising a tray onwhich a plurality of sample containers and buffer containers can bemounted, the autosampler being adapted to move vertically andhorizontally such that, when moved upward, the sample injection ends ofthe capillary array exposed from the constant temperature bath can beimmersed in a sample in the sample containers or a buffer in the buffercontainers, wherein the autosampler further comprises means for securingthe plurality of sample containers and buffer containers on the tray.

[0013] The autosampler comprises a guide and a stopper for retaining asample plate assembly and fixing it three dimensionally on the tray, thesample plate assembly including a microtiter plate for storing samplesand an adapter on which the microtiter plate is mounted.

[0014] Preferably, different types of the adapter are prepared fordifferent microtiter plates. Preferably, the tray includes a sensor fordetecting the shape of a bottom portion of the adapter in order toidentify the number of wells of the microtiter plate mounted on theadapter.

[0015] The invention further provides an autosampler provided in acapillary array electrophoretic device in which a capillary array ismounted with a sample injection end exposed outside a constanttemperature bath, the autosampler comprising a tray on which a pluralityof sample containers and buffer containers can be mounted, theautosampler being adapted to move vertically and horizontally such that,when moved upward, the sample injection ends exposed from the constanttemperature bath can be immersed in a sample in the sample containers ora buffer in the buffer containers, wherein the autosampler furthercomprises means for securing the plurality of sample containers andbuffer containers on the tray.

BRIED DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a perspective view of the exterior of an electrophoreticdevice according to the invention, with the door to a constanttemperature bath open.

[0017]FIG. 2 schematically shows the relationships among a constanttemperature bath of a capillary unit, a pump unit, and so on.

[0018]FIG. 3 schematically shows the overall arrangement of theelectrophoretic device of the invention.

[0019]FIG. 4 is an exploded view of a sample plate assembly.

[0020]FIG. 5 is a perspective view of the sample plate assembly.

[0021]FIG. 6 is a bottom view of the sample plate assembly.

[0022]FIG. 7 shows an example of a tray of an autosampler according tothe invention.

[0023]FIG. 8 shows another example of the tray of the autosampleraccording to the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0024] The invention will be hereafter described by way of examples inwhich a fluorescence-labeled DNA sample is used, with reference made tothe attached drawings.

[0025]FIG. 1 shows a perspective view of the exterior of anelectrophoretic device according to the invention, with the door to aconstant temperature bath open. In FIG. 1, a capillary array is not yetmounted. An electrophoretic device 100 includes a chassis 101 thathouses a constant temperature bath 102 equipped with a Peltier elementor the like for temperature control, a gel pump unit 103 for supplyingan electrophoresis medium to the capillaries in the capillary array, adetection unit 104, and an autosampler 105. A capillary array can bedisposed in the space inside the constant temperature bath. Theautosampler 105 is adapted such that a sample plate assembly and abuffer tank or the like, which will be described later, can be mountedon trays.

[0026]FIG. 2 illustrates the relationships among a capillary array unit201, the constant temperature bath 102, the gel pump unit 103, and thelike. One end of the capillary array unit 201 comprises sample injectionends that are inserted into hollow electrodes 202 made of hollowstainless steel pipes. Capillaries protrude slightly beyond the tips ofthe hollow electrodes 202. The gap between each capillary and eachhollow electrode 202 is sealed with glue so that no carryover of thesample or the like is caused. When a DNA sample is injected into thecapillaries, the sample injection ends of the capillaries are submergedin a solution containing the DNA sample. When the injected sample iselectrophoresed, the sample injection end is submerged in a buffersolution 205 and a voltage is applied between both ends of thecapillaries. In FIG. 2, the sample injection end is submerged in thebuffer solution 205, and the DNA sample is not shown.

[0027] On the other end of the capillary array unit 201 is formed acapillary head 203 which is adapted to be connected to the gel pump unit103 for the injection of a gel as a migration medium into the capillaryarray unit 201. When the gel, or the migration medium inside thecapillaries, is charged into the capillaries, a valve 206 is closed anda syringe 207 is pressed down, such that the gel inside the syringe 207can be injected into the capillary array unit 201. Duringelectrophoresis, the valve 206 is opened, and a voltage is appliedbetween the electrodes 202 immersed in the buffer 205 and a groundelectrode 209 immersed in a buffer 208. The capillary array unit 201 isalmost entirely housed inside the constant temperature bath 102, whichis of gas circulation type, except for its both end portions, so thatthe temperature of the unit can be maintained at a certain level. Adetector unit 204 is disposed outside the constant temperature bath 102for detecting fluorescence emitted by the fluorescence-labeled sampleseparated by electrophoresis in the capillaries.

[0028]FIG. 3 schematically shows an electrophoresis system. Eachcapillary in the capillary array unit 201 is made of a quartz pipe withan external diameter of 0.1 to 0.7 mm and an inner diameter of 0.02 to0.5 mm, and is coated with polyimide resin on the outside. A plurality(usually from several to several tens) of such capillaries are arrangedto form the capillary array unit 201. The capillary array unit 201includes a load header 301 for loading of samples into the capillariesby electrophoresis from a sample container containingfluorescence-labeled DNA samples or the like. The unit also includes thedetector unit (window unit) 204 in which the capillaries are arrangedand fixed in order of sample numbers on the load header 301, and thecapillary head 203 in which the plurality of capillaries are bundled andglued together. The load header 301 is provided with an electrode forapplying a migration voltage to the capillaries. The electrode isconnected to the hollow electrodes 202 in which the sample injection endof each capillary is inserted. The detector (window unit) 204 isprovided with an opening via which the capillaries arranged and retainedis irradiated with light, and another opening via which to pick up lightemission 302 from the capillaries.

[0029] The hollow electrodes 202 protruding from the load header 301 andthe sample injection ends of the capillaries of the capillary array unit201 are submerged in a sample container 311 containing thefluorescence-labeled DNA samples. The capillary head 203 on the otherend is attached to a buffer container 312 containing a buffer. Betweenthe buffer container 312 and the load header 301 is applied a highvoltage of about 15 kV from a high-voltage power supply 313, whereby thesamples in the sample container 311 are injected via the sampleinjection ends of the capillaries by electric field injection.Thereafter, the sample container 311 is removed, and the sampleinjection ends of the capillary array unit 201 are immersed in thebuffer, as shown in FIG. 2. A voltage is then applied between both endsof the capillaries to carry out electrophoresis of the samples.

[0030] The electrophoresed samples are detected by the detector unit(window unit) 204. Laser light 322 is emitted by a laser light source321. The laser light is reflected by a reflecting mirror 323, dividedinto two portions by a beam splitter 324, reflected by reflectingmirrors 325, and then condensed by condenser lenses 326 such that thecapillary array unit 201 is irradiated with the light from a directionparallel to the plane in which the capillaries are arranged. Thefluorescence-labeled samples that have electrophoretically migrated inthe gel filled in the capillaries are excited by the irradiation oflaser light 322, thereby emitting fluorescence 302. The fluorescence 302propagating in a direction substantially perpendicular to the plane inwhich the capillaries are arranged is rendered into parallel light by afirst lens 327, the image is divided by an optical filter and an imagesplitting prism 328, and then the image is focused on a CCD camera 330by a second lens 329. The measurement data detected by the CCD camera330 is processed by a processing and computing unit 331 to analyze thebase sequence or base length of the DNA samples. While in the figure thelaser light 322 irradiates the detector unit 204 from either sidethereof, the irradiation may occur on one side thereof.

[0031] The DNA sample or buffer solutions are transported by theautosampler 105 that is movable in X, Y and Z directions, such that thesample introduction end of each capillary in the capillary array unit201 is inserted into a desired container. The present invention providesa means for fixing the containers containing the DNA sample or buffers,for example, on the autosampler 105. Specific examples will be describedin detail below.

[0032] In order to reduce the load on the person who does the analysis,the samples to be analyzed are analyzed on a commercially availablemicrotiter plate. As the microtiter plate cannot be set on a tray of theautosampler as is, it is set on the tray as part of a four-layerstructure sample plate assembly consisting of a plate adapter, theplate, a septum, and a septum holder. There are various microtiterplates available with corresponding adapters, so that any type of platecan be mounted on the autosampler. Two types of microtiter plates areavailable, one with 8×12=96 wells and the other with 16'24=384 wells.The electrophoretic device of the invention can accommodate two sets ofthe aforementioned sample plate assemblies simultaneously, so that amaximum of 384×2=768 samples can be continuously analyzed.

[0033] FIGS. 4 to 6 show a sample plate assembly with a 96-wellmicrotiter plate. FIG. 4 shows an exploded view, FIG. 5 shows aperspective view of the sample plate assembly as assembled, and FIG. 6shows a bottom view.

[0034] The sample plate assembly is made up of a plate adapter 401, amicrotiter plate 402, a septum 403, and a septum holder 404. The plateadapter 401 is the mount with which the microtiter plate 402 can be seton the tray of the autosampler 105. The septum 403 is made of siliconrubber and is formed with projections whose tips are adapted to enterinto the individual wells on the microtiter plate 402. These tips areprovided with cuts for the passage of the tips of the capillaries. Theseptum 403 has the function of preventing sample evaporation and that ofwiping off samples or the like that have attached to the capillary tips.The septum holder 404 is a component for securing the microtiter plate402 and the septum 403 to the adapter 401.

[0035]FIG. 5 shows a sample plate assembly 500 assembled from the septumholder 404, septum 403, microtiter plate 402 and plate adapter 401. FIG.6 shows the sample plate assembly from which the septum holder 404 hasbeen detached. The septum holder 404 also has the function of correctingthe shape of the microtiter plate 402 and securing it onto the adapter401 correctly, as the microtiter plate 402 is used in a thermal processcalled PCR (Polymerase Chain Reaction), which is a pre-processing forthe samples, and could be deformed under certain conditions. At thebottom of the plate adapter 401 is provided a light-shielding plate 605or a notch 606 for identifying the type of the plate adapter with aphoto interrupter. The plate adapter 401 also has guides 715 and 716formed at different heights on either lengthwise side thereof.

[0036] The septum holder 404 has two nails 601 on either side, as shownin FIG. 6, which are adapted to be hooked with a flange 603 on theadapter 401, so that the holder can be simply mounted on the adapter 401without bothering the analyzer. As a result, the septum holder 404 couldpossibly be displaced along the length of the plate adapter 401 whenthey are fitted together. If the septum holder 404 is thus incorrectlysecured to the plate adapter 401, the openings of the septum holder 404through which the capillaries are passed would not coincide with thewells in the microtiter plate 402, which would damage the capillaries.To prevent this, projections 602 are provided at the nails 601 at fourlocations on the septum holder 404, whereby the nails 601 cannot engagewith the flange 603 unless the projections 602 are matched up withguides 604 on the adapter, thus limiting the manner in which the septumholder 404 can be mounted on the plate adapter 401. Thus, the analyzercan mount the septum holder 404 on the plate adapter 401 without payingany particular attention, and the problem of mounting it at a wrongposition can simultaneously be eliminated.

[0037] The autosampler of the invention can accommodate different plates(heights) by means of the adapter. Several types of microtiter plateswith 96 wells are commercially available that can be used with theelectrophoretic device of the invention, with different shapes, sizesand depths of the wells depending on the manufacturers. If the minimumsample amount for the electrophoretic device of the invention is set tobe at 10 μl, the height from the bottom of the well to the sample levelcan be about 2.5 mm, for example, in the case of some commerciallyavailable 96-well microtiter plates. Thus, the capillaries must beinserted to the depth of about 1 mm from the bottom of the well if thesamples are to be introduced into the capillaries in a reliable manner.However, the height of the bottom of the well greatly varies dependingon each microtiter plate, so that, if no distinctions are made betweenthe individual microtiter plates, the tip of the capillaries could hitthe bottom and be damaged, or it would not reach the samples and thusfail to have the samples introduced into the capillaries.

[0038] Thus, in order to correct the height of the bottom of the well orthe position of the central axis among the microtiter plates fromvarious manufacturers, plate adapters are prepared that are adapted toindividual microtiter plates. By using them in various combinations, anymicrotiter plate with 96 wells can be positioned on the tray on theautosampler at the same location in terms of the central axis of thewell and the height of the bottom. Accordingly, it is only necessary forthe autosampler to recognize the number of the wells (96 or 384) on thesample plate assembly mounted thereon and select the control methodaccordingly. In this way, the autosampler can be moved by the samecontrol method at all times regardless of the type of the 96-wellmicrotiter plate mounted.

[0039] While it is not easy to distinguish the 96-well microtiter platesfrom the various manufacturers at a glance, the individual plate adapteris provided with features such that it will not be attached to a wrongplate adapter or attached in a wrong direction. For example, in the caseof the microtiter plate 402 shown in FIG. 4, one of the four corners iscut off. The direction or size of the cutoff varies for individualmicrotiter plates, and the plate adapter 401 is also shaped tocorrespond to each cutoff. Thus, the chances of attaching the microtiterplate to a wrong plate adapter or in a wrong direction can beeliminated.

[0040] The autosampler of the invention can deal with 96/384 with thesame structure. Two sets of the plate adapter for 96-well microtiterplates and the plate adapter for 384-well microtiter plates can bemounted on the tray on the autosampler in any combination selected bythe user in light of the purpose of analysis.

[0041]FIG. 7 shows an example of the tray of the autosampler of theinvention. A tray 700 in the illustrated example is capable of mountingtwo sets of sample plate assemblies and four sets of tanks for storingbuffers or water, for example. As many of these assemblies or tanks asnecessary for electrophoresis may be mounted.

[0042] On either side of the location for the mounting of the sampleplate assembly is provided a horizontal guide groove 701. Sample plateassemblies 710 and 711 (which are drawn in a simplified form in FIG. 7but which actually have a multilayer structure, as shown in FIG. 5) areset on the tray 13 in the following manner. They are slid horizontallyfrom the outside of the tray 13 such that guides 715 and 716horizontally provided on either side of each assembly are engaged withthe guide grooves 701 on the tray 700. Thus the sample plate assemblies710 and 711 can be secured on the tray 700 in vertical (Z) direction.The sample plate assemblies 710 and 711 are fixed in the direction alongthe guide grooves 701 of the tray 700 by closing a cover 702 provided onthe tray 700 once the assemblies are inserted to the end of the grooves701. The cover 702 is secured to the side of the tray 700 by means of anail, screw, or magnet, for example, provided at the tip of the cover.

[0043] At the location of the tray 700 where tanks are disposed isprovided a gate-shaped frame 731 and a recessed portion 732. Tanks 720to 723 are mounted on the tray 700 by passing through the gate-shapedframe 731 and then having the end of each tank inserted into therecessed portion 732. Thereafter, a cover 734 is closed so as torestrict the movement of the tanks out of the 731. Thus, the tanks 720to 723 are secured in place in vertical and horizontal directions.

[0044] Thus, the sample plate assemblies 710 and 711 and the tanks 720to 723 are secured in place on the tray 700 in all of the X, Y and Zdirections, thereby eliminating the problems of the microtiter plates,the tanks, or the septa thereon being lifted when the sampleintroduction end of the capillary array unit 201 is moved up or down inthe microtiter plates or tanks in response to the up/down movement ofthe autosampler. Accordingly, there is no need to provide a separatemechanism for pushing the sample plate assemblies or the tanks againstthe tray, such as the stripper plate.

[0045] On the tray 700 are mounted two photo interrupters 740 for eachlocation where the sample plate assembly is mounted, for a total of fourphoto interrupters. These photo interrupters are used for automaticallyidentifying microtiter plates with different numbers of wells. Thepresent embodiment is adapted for two kinds of microtiter plates with 96and 384 wells, and which microtiter plates are mounted is automaticallyidentified.

[0046] Different types of adapter 401 are prepared for the two types ofmicrotiter plates, and each adapter is provided with a light-shieldingplate at a different location. As the adapter is set on the tray 700,the light-shielding plate blocks the light emitted by one of the twophoto interrupters 740 on the tray 700. Further, the guide grooves 701on the sides of the tray 700 are provided at different heights so as tofix the direction in which the adapter is mounted. Similarly, the guides715 and 716 on the sides of the adapter 401 are provided at differentheights to be matched with the guide grooves on the tray 700. Therefore,the two types of adapters can be set on the tray 700 only in onedirection, thereby making sure that the adapters will not bemisidentified by the photo interrupters 740. Based on signals from thephoto interrupters, which type of microtiter plate is mounted can beautomatically identified, whereby the autosampler can be operated whileswitching the distance of its travel in accordance with the pitch ofwells.

[0047] The arrangement of the sample plate assemblies and tanks, thedirection in which they are slid, the direction of opening or closing ofthe covers, and so on, are not limited to those shown in FIG. 7, andthey may be modified in accordance with the arrangement of theautosampler in the electrophoretic device or the size of the space thatis provided in areas surrounding the tray.

[0048]FIG. 8 shows another example of the tray for the autosampler inaccordance with the present invention. A tray 800 in this example iscapable of mounting two sets of sample plate assemblies 810 and 811 andfour sets of tanks 820 to 823, as the tray 700 shown in FIG. 7 is. Thetray 800 differs from the tray 700 in the manner in which the sampleplate assemblies and tanks are mounted and secured. Other points aresimilar to those of the example of FIG. 7 and are therefore notdescribed.

[0049] The sample plate assemblies 800 and 801 and the tanks 820 to 823are set on the tray 800 from above along guides thereof. In this case,the vertical walls on the tray 800 surrounding the locations where thesample plate assemblies and the tanks are to be mounted function as theguides. No special guides are required on the sides of the sample plateassemblies 800 and 801, in contrast to the example of FIG. 7. Once seton the tray 800 from above, the assemblies 800 and 801 and the tanks 820to 823 are fixed in place in X and Y directions. A clip 830 is thenattached from above the tray 800 in such a manner as to cover the sampleplate assemblies 800 and 801 and the tanks 820 to 823, thereby securingthe assemblies and tanks in Z direction.

[0050] In the example shown in FIG. 8, the sample plate assemblies andtanks are all fastened with a single clip 830. However, the clip may bedivided into two portions, one for the sample plate assemblies and theother for the tanks, for example. Further, while in the example of FIG.8 the clip 830 is an independent part from the tray 800, an integral,openable clip/tray cover may be employed. Such an integral cover may ofcourse be further divided into multiple covers.

[0051] Industrial Applicability

[0052] In accordance with the invention, sample containers, buffercontainers or the like can be easily mounted on a tray of an autosamplerand fixed thereon in X, Y and Z directions. As the invention does notrequire the use of the conventional stripper plate, the structure of thedevice can be simplified, and the length of the capillary array that isexposed outside a constant temperature bath can be minimized, thusenhancing analysis accuracy.

1. A capillary array electrophoretic device comprising: a capillaryarray made up of a plurality of capillaries with their sample injectionends arranged in order; a constant temperature bath for storing thecapillary array with the sample injection ends disposed downward andexposed; and an autosampler comprising a tray on which a plurality ofsample containers and buffer containers can be mounted, the autosamplerbeing adapted to move vertically and horizontally such that, when movedupward, the sample injection ends exposed from the constant temperaturebath can be immersed in a sample in the sample containers or a buffer inthe buffer containers, wherein the autosampler further comprises meansfor securing the plurality of sample containers and buffer containers onthe tray.
 2. The capillary array electrophoretic device according toclaim 1, wherein the autosampler comprises a guide and a stopper forretaining a sample plate assembly and fixing it three dimensionally onthe tray, the sample plate assembly including a microtiter plate forstoring samples and an adapter on which the microtiter plate is to bemounted.
 3. The capillary array electrophoretic device according toclaim 2, wherein different types of the adapter are prepared fordifferent microtiter plates.
 4. The capillary array electrophoreticdevice according to claim 2 or 3, wherein the tray includes a sensor fordetecting the shape of a bottom portion of the adapter in order toidentify the number of wells of the microtiter plate mounted on theadapter.
 5. An autosampler provided in a capillary array electrophoreticdevice in which a capillary array is mounted with a sample injection endexposed outside a constant temperature bath, the autosampler comprisinga tray on which a plurality of sample containers and buffer containerscan be mounted, the autosampler being adapted to move vertically andhorizontally such that, when moved upward, the sample injection endexposed from the constant temperature bath can be immersed in a samplein the sample containers or a buffer in the buffer containers, whereinthe autosampler further comprises means for securing the plurality ofsample containers and buffer containers on the tray.
 6. The autosampleraccording to claim 5, further comprising a guide and a stopper forretaining a sample plate assembly and fixing it three dimensionally onthe tray, the sample plate assembly including a microtiter plate forstoring samples and an adapter on which the microtiter plate is mounted.7. The autosampler according to claim 6, wherein different types of theadapter are prepared for different microtiter plates.
 8. The autosampleraccording to claim 6 or 7, wherein the tray includes a sensor fordetecting the shape of a bottom portion of the adapter in order toidentify the number of wells of the microtiter plate mounted on theadapter.